info.debatty.java.stringsimilarity

Class QGram

java.lang.Object

info.debatty.java.stringsimilarity.QGram

All Implemented Interfaces:

StringDistance, Serializable

public class QGram
extends Object
implements StringDistance

Q-gram distance, as defined by Ukkonen in "Approximate string-matching with q-grams and maximal matches". The distance between two strings is defined as the L1 norm of the difference of their profiles (the number of occurences of each n-gram): SUM( |V1_i - V2_i| ). Q-gram distance is a lower bound on Levenshtein distance, but can be computed in O(m + n), where Levenshtein requires O(m.n).

Author:

Thibault Debatty

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected int	k

Constructor Summary

Constructors

Constructor and Description
QGram()
QGram(int n) Q-gram similarity and distance.

Method Summary

Methods

Modifier and Type	Method and Description
double	distance(String s1, String s2)
int	getK() Return k, the length of k-shingles (aka n-grams)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

k

protected final int k

Constructor Detail

QGram

public QGram(int n)

Q-gram similarity and distance. Defined by Ukkonen in "Approximate string-matching with q-grams and maximal matches", http://www.sciencedirect.com/science/article/pii/0304397592901434 The distance between two strings is defined as the L1 norm of the difference of their profiles (the number of occurence of each k-shingle). Q-gram distance is a lower bound on Levenshtein distance, but can be computed in O(|A| + |B|), where Levenshtein requires O(|A|.|B|)

Parameters:

n -

QGram

public QGram()

Method Detail

distance

public double distance(String s1,
              String s2)

Specified by:

distance in interface StringDistance

getK

public int getK()

Return k, the length of k-shingles (aka n-grams)

Returns: